-
The BladeForums.com 2024 Traditional Knife is ready to order! See this thread for details: https://www.bladeforums.com/threads/bladeforums-2024-traditional-knife.2003187/
Price is$300$250 ea (shipped within CONUS). If you live outside the US, I will contact you after your order for extra shipping charges.
Order here: https://www.bladeforums.com/help/2024-traditional/ - Order as many as you like, we have plenty.
S30V Vs. AUS-8
- Thread starter bzzhewt
- Start date
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
It was promoted on the basis of impact toughness along the grain and some claimed that this made it a much tougher steel.
-Cliff
-Cliff
So what steel would be tougher?Cliff Stamp said:
Would "tougher" mean something with less hardness and more flexibility?
Please explain toughness in simple terms.
The way I understand it, toughness means less brittle and a bit softer, so as not to chip or snap.
Strangth would be more hardness to a certain degree, but would be less flexible and more brittle.
The harder a steel is, the stronger and more edge retention, but loses toughness. If you soften it, it get a bit tougher, as its more flexible.
Am I close?
But what is the definition of toughness?
I ALMOST understand, but still get confused!
Help!
Thanx for bearing with me.
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
bzzhewt said:
Pretty much exact, there is a slight complexity to the equation which is that the relationship between toughness and hardness isn't linear. Most steels have a toughness peak, as you move up or down in hardness around this point the toughness will decrease.
In regards to edge retention, this is dependent on pretty much all the various steel properties, strength, toughness, ductility, wear resistance, and corrosion resistance. Which ones are important depends on what is being cut and how.
Strength keeps the edge from rolling/deforming, ductility and toughness keeps the edge from cracking, wear resistance keeps metal from being scraped off the edge and corrosion resistance prevents the edge from being consumed by oxidization.
For example in chopping wood, you would not want to maximize hardness because at some point the edge would just crack apart because the toughness is too low. However if you are cutting cardboard then the edge is going to blunt mainly by deformation and wear so you want a really hard and high wear steel.
-Cliff
- Joined
- Oct 14, 1998
- Messages
- 2,157
bzzhewt,bzzhewt said:
I have a 2 folders made with 52100.
The first is a liner lock made by MS Ed Caffrey. This a serious working knife, not a fancy wall hanger. It is differentially heat treated and convex ground with G10 scales and titanium liners. It cuts like crazy! I strongly recommend this knife if you want a serious no-nonsense work knife.
http://www.caffreyknives.net/
The second knife is a beautiful slip joint made by MS Bailey Bradshaw. It has stainless double bolsters and elephant ivory scales. It is a very classy slip joint that I'm sure would work great, but I'm not going to test it.
http://www.bradshawcutlery.com/
I've been told MS Mike Vagnino also makes a good working folder from 52100.
http://www.mvknives.com/
- Joined
- Mar 7, 2005
- Messages
- 1,063
Chuck,
Great suggestoins in knives. Those Master Smiths make an incredible. I really wish I could afford a Cafferry Progession folder (pic from his site):
That is just a great looking folder. Given Caffery's reputation for excellent geometry and heat treat I bet it cuts as nice as it looks.
Cliff:
A nice, concise explanation.
Great suggestoins in knives. Those Master Smiths make an incredible. I really wish I could afford a Cafferry Progession folder (pic from his site):
That is just a great looking folder. Given Caffery's reputation for excellent geometry and heat treat I bet it cuts as nice as it looks.
Cliff:
A nice, concise explanation.
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
To give some credit :
Alvin argued for hardness in edge retention and fine grain structure in opposite to the edge holding = wear resistance theory that is most popular, even today. Mike Swaim and Alvin's other field testors evaluated his claims vs many knives including Bos hardened ATS-34.
Later I discussed this with Wilson who had reached a similar conclusion in that unless the hardness is high enough, the wear resistance is of little value because if the edge is too weak and loses alignment it will be dull even if it isn't worn at all. He tested some extreme steels (S90V) at really low HRC's and noted the performance bottomed out, as the edge just rolled.
Many others noted similar in just use, Hilton Yam for example was one of the early ones aside from Mike, and noted that while Cold Steel's AUS-8A blades were very sharp, the edges cold just roll readily on cuts on hard targets, lots of others I would assume reached similar conclusions, but didn't discuss it on line. Lee talkes about it in his sharpening book.
Busse also developed his ideas about edge retention for a radically different class of knives than Alvin and Phil, and he concluded that toughness was critical as you have to prevent micro-cracking. Busse and Glesser were the first two in the industry I heard talk about examining edges under magnification to study performance. J.J. did similar in regards to developing his ideas on sharpening.
After talking to all these guys and doing work on my own I felt I had a decent grasp and sketched out an outline similar to the above and sent it to Wilson, he thought it was solid and pointed me to an article he had written for one of the mags years ago which was similar (and better written).
A few other guys to note, R.J. Martin is someone you really need to talk to if you are serious about sharpening, Ray Kirk grinds some really sharp knives and is quite willing to tell you exactly how he does it, no BS or secret methods which I think is very telling, the minute someone starts to get vague I lost all interest. Goddard also has done a hell of a lot of test cutting and abrasive comparisons and is willing to talk about it.
-Cliff
Alvin argued for hardness in edge retention and fine grain structure in opposite to the edge holding = wear resistance theory that is most popular, even today. Mike Swaim and Alvin's other field testors evaluated his claims vs many knives including Bos hardened ATS-34.
Later I discussed this with Wilson who had reached a similar conclusion in that unless the hardness is high enough, the wear resistance is of little value because if the edge is too weak and loses alignment it will be dull even if it isn't worn at all. He tested some extreme steels (S90V) at really low HRC's and noted the performance bottomed out, as the edge just rolled.
Many others noted similar in just use, Hilton Yam for example was one of the early ones aside from Mike, and noted that while Cold Steel's AUS-8A blades were very sharp, the edges cold just roll readily on cuts on hard targets, lots of others I would assume reached similar conclusions, but didn't discuss it on line. Lee talkes about it in his sharpening book.
Busse also developed his ideas about edge retention for a radically different class of knives than Alvin and Phil, and he concluded that toughness was critical as you have to prevent micro-cracking. Busse and Glesser were the first two in the industry I heard talk about examining edges under magnification to study performance. J.J. did similar in regards to developing his ideas on sharpening.
After talking to all these guys and doing work on my own I felt I had a decent grasp and sketched out an outline similar to the above and sent it to Wilson, he thought it was solid and pointed me to an article he had written for one of the mags years ago which was similar (and better written).
A few other guys to note, R.J. Martin is someone you really need to talk to if you are serious about sharpening, Ray Kirk grinds some really sharp knives and is quite willing to tell you exactly how he does it, no BS or secret methods which I think is very telling, the minute someone starts to get vague I lost all interest. Goddard also has done a hell of a lot of test cutting and abrasive comparisons and is willing to talk about it.
-Cliff
I am concerned primarily with hardness for a few reasons.
First, it is the thing most directly controlled when making a knife. You can pick from different steels, but you have to pick one of them. Hardness can be adjusted to exactly what you want. You don't "choose" any other properties save for choosing another steel entirely or sacrificing hardness for toughness. So in my mind I approach the issue as "we have a piece of steel and we want to make a knife. Once design and materials are chosen, our biggest question is hardening and tempering."
Second, even early experience told me that harder blades just plain worked better. I throught sharpening was a pain in the butt until I got some better knives, and they stayed sharp longer too. Harder blades seemed to make everything better.
Third, other people ahead of me (you, Alvin, and Mike among a few others I have forgotten) who had already spent many years tesing knives under real conditions agreed, and were actually even more emphatic than I was, most likely due to more experience and deeper knowledge than I had.
Fourth, while I know all steel characteristics are important, low hardness seems like a plague in the population of production knives while strength, wear resistance, etc, are often fairly strong points (hard work testing shows not all are created equal, but even decades in the past there were decently durable steels available, so there was not really a "mystery" involved). I haven't used too many knives for which wear resistance was a big issue. The problem with poorly-performing blades is almost always a burred and deformed edge after short use much more so than simple wearing down.
Fifth, my own testing almost never involves use that would result in fractures or major damage, except for the worst of steels. Mostly I just test for edge retention during extended but not extreme work. Characteristics like strength and toughness just don't show through in many uses, while hardness and wear resistance can be observed for almost any job done for more than a few seconds. It's easy to say "it has to be strong enough not to break," but hardness and wear resistance are much more of a "how much damage" than a "breaks or doesn't break." No hardness is enough to completely avoid bending and no wear resistance is enough to completely avoid wear, so how do we quantify, with even the most subjective numbers at all, what makes a "good enough" knife for a job?
This brings us to my next goal, which would be stating exactly what level of hardness would be the minimum reasonable rating for a specific level of wear resistance. I feel I have given the concept enough testing to say that, combined with the lengthy experience of others, the hardness:wear ratio is a major way to determine how well a knife will perform. If we were to test and report this in terms of hard data, we could tell a manufacturer with accuracy exactly how hard a steel had to be in relation to its wear resistance. They could then decide how hard to make a specific knife based on that, or they might even reject a steel formula because, when hardened to the proper ratio to make a good blade, it cracks under a desired work load.
It may be that the CATRA "life tester" needs to be examined. Manufacturers seem happy to rely on it, but I wouldn't be the first to have second guesses about certain aspects of it. Too bad none of us have one to experiment with, because I would really like to see it used with a slight tild to the tested blade since real life is never perfect. I think a tilt matching the angle of the edge bevel would be a fair test because a "perfect" blade would still enjoy the cutting ability from its sharpness (and more of an angle would simulate a blunter edge). But deformed edges would quickly show their drop in cutting ability.
We don't need to solve the CATRA mystery (as to why blades we hate often get good results) to learn about steel, but we might if we wanted to convince a modern mass market manufacturer to start making better knives.
I agree but I have not experienced such issues that I know of. Maybe I need to get a microscope and take a closer look. I definitely think this becomes an issue of how stressful is the job in question while hardness:wear affects any job. Maybe micro-cracking is more common than I know. I might dig out my old pocket microscope if I can find it and take a look.
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
Carl64 said:
And ironically it is the part often given the least R&D.
As steels get harder to machine you need to be more careful about optomizing geometry. In general, if machinability is a concern when sharpening either the steel is a poor choice for the knife or it is ground really unsuitable for the tasks the knife is used for.
Alvin demonstrated this twenty years ago and people still say things like D2 is hard to sharpen because it has a low machinability referring to the difficulty in removing a lot of material. If you have to do this when sharpening a knife then something is seriously wrong.
I can sharpen Alvin's blades and the hacked jobs I have made similar far far faster than production blades with edges which are 10x thicker in cross section. When your edge is ~0.005" thick and 5 degrees per side, there is a minute amount of material removed when sharpening.
Yeah, I don't think I have ever seen a still crisp but worn edge. Even a cheap 10x magnifier turned into the edge straight on would destroy the wear resistance = edge retention myth. Just cut some cardboard and look at the waves it produces to knife edges. Yes steel is strong, but when it is a thousand of an inch thick it doesn't take much force to bend it anymore.
It would be informative if this was examined in detail. For example take S90V blades from 57-63 HRC and compare it on cardboard and hemp rope to an ATS-34 blade at 60 HRC. This is what I would be doing if I was a maker.
[CATRA]
On an interesting note, ask them exactly what it means, does it mean you can cut 25% more material, or the knife is 25% blunter after cutting a similar amount of material, and what happens if you compare at a different point, does the percentage increase or decrease? Do the results get better or worse if you adjust the edge angle? Can you adjust the angle profile on 420HC so it out CATRA's S30V when both are equally sharp?
A lot of people are just happy to use a statistic which allows them to promote their knives and don't even understand what it actually measures. People were promoting "1000 lbs of pressure" and other similar meaningless lock statistics for a long time which are actually complete gibberish because the units are mixed up and you need to examine torque not force/pressure. It would be like saying "Man it is really hot out today, it must be fifty grams long."
The biggest problem is lack of load variance, if you can exert pressure straight down on a blade and the media being cut is rigid there is little side load, people can't do this and it is why CATRA scores are a horribly unscientific way to examine edge retention for knives used by people. You are measuring something with great precision which has little relevance to the problem. All the precision in the world doesn't help with no accuracy.
[chipping]
On stainless, it is a major form of blunting on cardboard. The edges will roll/deform, but they also lose huge pieces. It makes a huge difference in resharpening.
-Cliff
Here are some threads relating to different types of knife steel. Much depends not only on the type of steel but also the heat treatment, grind, shape, and use.
http://www.ajh-knives.com/metals.html
http://www.huntingblades.com/tyofstusinkn.html
http://www.ajh-knives.com/metals.html
http://www.huntingblades.com/tyofstusinkn.html
